Polyesters modified by a combination of ionomer and organic acid salts

ABSTRACT

Disclosed is a thermoplastic composition comprising a poly(trimethylene terephthalate) and about 0.2 to about 30 weight % of a modifier comprising organic acid and an ionomer derived from an ethylene acid copolymer in which the combined acid moieties of the organic acid and acid copolymer are at least partially neutralized with cations of magnesium, calcium, zinc, or a combination thereof.

This application claims priority to U.S. provisional application Ser.No. 61/023220, filed Jan. 24, 2008; the entire disclosure of which isincorporated herein by reference.

This invention relates to poly(trimethylene terephthalate) orpoly(tetramethylene terephthalate) composition, shaped articletherewith, and method for reducing melt viscosity of poly(trimethyleneterephthalate) or poly(tetramethylene terephthalate) composition.

BACKGROUND OF THE INVENTION

Thermoplastic polymers are commonly used to manufacture various shapedarticles that may be utilized in applications such as automotive parts,food containers, signs, and packaging materials. Shaped articles may beprepared from polyester by a number of melt extrusion processes known inthe art, such as injection molding, compression molding, blow molding,and profile extrusion.

The most common polyester currently used is polyethylene terephthalate(PET). Due to recent trends toward sustainability and reduced use ofpetroleum, alternatives to PET are being investigated. Poly(trimethyleneterephthalate), herein abbreviated 3GT, also referred to as PTT orpolypropylene terephthalate, may be useful in many materials andproducts in which polyesters such as PET are currently used, for examplemolded articles. 3GT has properties including a semi-crystallinemolecular structure.

British Patent 578097 disclosed the synthesis of 3GT in 1941. 3GT may beprepared using 1,3-propanediol derived from petroleum sources or frombiological processes using renewable resources (“bio-based” synthesis).The ability to prepare 3GT from renewable resources makes it anattractive alternative to PET. 3GT produced from renewable sources of1,3-propanediol is commercially available from E.I. du Pont de Nemoursand Company (DuPont) under the tradename SORONA. DuPont pioneered a wayto produce the 1,3-propanediol from renewable resources including cornsugar.

The melt viscosity or intrinsic viscosity (IV) of 3GT varies dependingon how it is prepared and is roughly correlated to the molecular weight.Previous applications often used 3GT polymerized to lower IV. Thisapproach may lead to low impact performance (impact resistance), and hascritical moisture requirements because of the low molecular weight ofthe polymer. The low IV resins are predominantly used inglass-reinforced materials, which to some degree mitigate the effect oflow IV on impact performance.

Use of reinforcements may lead to higher viscosity, poor surface gloss,and poor scratch and mar resistance and other esthetic effects. Theincreased interest in 3GT as a replacement for PET is prompting the useof 3GT in applications that do not permit the use of reinforcingmaterials. These applications using unreinforced 3GT may have problemswith inadequate impact resistance and/or moisture concerns when 3GT withlower IV is used.

Another polyester of interest is poly(tetramethylene terephthalate),herein abbreviated 4GT, also referred to as PBT or polybutyleneterephthalate.

Compositions comprising poly(trimethylene terephthalate) and athermoplastic polyester have been disclosed (e.g., JP2614200,JP2004-300376 and JP2006-290952).

Monofunctional organic acids are known to interchange with polyester,leading to lower molecular weight polymers. Similarly, salts of organicacids are known to cause molecular weight loss.

Using higher viscosity polyester may improve impact resistance, but thehigh viscosity may lead to processing difficulties. Higher viscositypolymers may decompose at higher temperatures and may have thermallimits that preclude viscosity reduction by operating at very hightemperatures.

Toughening (increased impact resistance) may also be useful for articlesprepared from the compositions. Toughening polyester has been achievedusing an ionomer modifier, an epoxide-containing copolymer such asethylene/n-butyl acrylate/glycidyl methacrylate (EBAGMA) (e.g.,WO85/03718, WO2007/089644, and U.S. Pat. No. 5,091,478). See also,JP2614200, JP2004-300376, and JP2006-290952.

Methods to lower viscosity and thereby improve injection molding of 3GTcompositions, while simultaneously maintaining as much “bio-based”content as possible, are desirable. Increasing toughness and/or impactresistance is also desirable.

SUMMARY OF THE INVENTION

The invention provides a thermoplastic composition comprising,consisting essentially of, or prepared from, based on the weight of thethermoplastic composition, about 70 to about 99.8% of a polyester and amodifier wherein

the polyester is poly(trimethylene terephthalate) or poly(tetramethyleneterephthalate);

the modifier comprises at least one aliphatic, monofunctional organicacid, at least one ionomer derived from an ethylene acid copolymer, andoptionally at least one ethylene ester copolymer;

the organic acid has 4 to 36 carbon atoms, optionally substituted with aC₁₋₈ alkyl group;

the ethylene acid copolymer comprises copolymerized comonomers ofethylene, a copolymerized comonomers of at least one C₃₋₈α,β-ethylenically unsaturated carboxylic acid, and optionally acopolymerized comonomer of at least one C₃₋₈ α,β-ethylenicallyunsaturated carboxylic acid ester;

the ethylene ester copolymer wherein comprises, based on the weight ofthe ethylene ester copolymer, (i) about 20 to about 95% of copolymerizedunits of ethylene, (ii) 0 to about 25% of copolymerized units of atleast one ester of the formula CH₂═C(R¹)CO₂R², and (iii) 0 to about 80weight % of copolymerized units of at least one ester of the formulaCH₂═C(R³)CO₂R⁴; (ii) and (iii) cannot both be 0 weight %; R¹ is hydrogenor an alkyl group having 1 to 6 carbon atoms; R² is a glycidyl group; R³is hydrogen or an alkyl group having 1 to 8 carbon atoms; and R⁴ is analkyl group having 1 to 8 carbon atoms;

from about 75% to about 100% of the combined acid moieties in themodifier are neutralized to form salts with metal cations; and

the cations comprise at least about 75 equivalent % of magnesium,calcium, zinc, or combination thereof.

Optionally, the longest carbon chain of the acid is substituted with 1-3substituents independently selected from C₁ to C₈ alkyl groups, Theethylene acid copolymer may comprise about 3 to about 35 weight % ofC₃₋₈ α,β-ethylenically unsaturated carboxylic acid, and 0 to about 30weight % of C₃₋₈ α,β-ethylenically unsaturated carboxylic acid ester.

This invention also provides shaped articles comprising or prepared fromthe composition described above.

The invention also provides method that can be used for reducing themelt viscosity of a polyester composition, which comprises melt mixingthe first 3GT or first 4GT composition with a modifier to provide afinal composition wherein the polyester composition and the modifier areeach as disclosed above; the final composition comprises, consistsessentially of, or consist of, based on the total weight of the finalcomposition, about 70 to about 99.8 weight % of the 3GT or 4GT polymer;about 0.2 to about 30 weight % of the combination of the organic acidand the ethylene acid copolymer; and optionally about 5 to 15 weight %of the ethylene ester copolymer.

The melt viscosity of the final composition may be at least 10% lessthan that of the 3GT or 4GT polymer composition and the number averagemolecular weight of the final composition may be at least 85% of that ofthe 3GT or 4GT polymer composition.

DETAILED DESCRIPTION OF THE INVENTION

Entire disclosures of all references are incorporated by reference.

Tradenames or trademarks are in uppercase.

All percentage is weight %, unless otherwise indicated.

“Copolymer” refers to polymers comprising copolymerized units resultingfrom copolymerization of two or more comonomers. “Dipolymer” refers topolymers consisting essentially of two comonomer-derived units and“terpolymer” means a copolymer consisting essentially of threecomonomer-derived units.

The melt viscosity of 3GT or 4GT polyesters may be lowered by theaddition of minor amounts of a combination of magnesium-, zinc- orcalcium-containing ethylene acid ionomer and organic acid salt (atlevels from 0.2 to 30% for the combination), resulting in higher meltflow. Compared to unmodified 3GT or 4GT, the modified blends have halfto a third the melt viscosity. Combinations of ethylene acid ionomersand organic acid salts with sodium or potassium cations increase meltflow, but as a result of reducing the molecular weight of the polyesterand accordingly compromising the mechanical properties of thecomposition. In contrast, magnesium-, zinc- or calcium-containingcompositions provide increased melt flow without reducing molecularweight.

3GT polyester blends containing ionomers may be toughened by theaddition of ethylene/alkyl acrylate copolymers, ethylene/alkylacrylate/epoxy copolymers or combinations thereof.

A “3GT homopolymer” means any polymer consisting essentially of repeatunits of trimethylene terephthalate and is substantially derived fromthe polymerization of 1,3-propanediol with terephthalic acid, or derivedfrom the ester-forming equivalents thereof (e.g., any reactants whichmay be polymerized to ultimately provide a polymer of poly(trimethyleneterephthalate).

A “3GT copolymer” means any polymer comprising (or derived from) atleast about 80 mole percent trimethylene terephthalate and the remainderof the polymer being derived from monomers other than terephthalic acidand 1,3-propanediol, or their ester forming equivalents. Ester-formingequivalents include diesters such as dimethylterephthalate. Examples of3GT copolymers include copolyesters synthesized from 3 or morereactants, each having two ester forming groups. For example, a 3GTcopolymer (co3GT) may be prepared by reacting 1,3-propanediol,terephthalic acid, and one or more comonomers selected from linear,cyclic, and branched aliphatic dicarboxylic acids having 4 to 12 carbonatoms such as butanedioic acid, pentanedioic acid, hexanedioic acid,azelaic acid, sebacic acid, dodecanedioic acid,1,4-cyclohexane-dicarboxylic acid, or ester-forming equivalents thereof;aromatic dicarboxylic acids other than terephthalic acid having 8 to 12carbon atoms such as phthalic acid, isophthalic acid or2,6-naphthalenedicarboxylic acid; linear, cyclic, and branched aliphaticdiols other than 1,3-propanediol having 2 to 8 carbon atoms such asethanediol, 1,2-propanediol, 1,4-butanediol, or 1,4-cyclohexanediol; andaliphatic and aromatic ether glycols having 4 to 10 carbon atoms such ashydroquinone bis(2-hydroxyethyl) ether. A co3GT may be prepared from apoly(ethylene ether) glycol having a molecular weight below about 460,such as diethylene ether glycol, methoxypolyalkylene glycol, diethyleneglycol, and polyethylene glycol. The comonomer may be present in thecopolymer at a level of about 0.5 to about 15 mol %, and may be presentat a level of up to about 30 mol %.

The 3GT copolymer may comprise other comonomers and such comonomers maybe copolymerized into the copolymer chain in minor amounts, e.g., up toabout 10 mol %, or up to about 5 mol %. Examples of such othercomonomers include functional comonomers such as 5-sodiumsulfoisophthalate, which can be in an amount of about 0.2 to about 5 mol%. About 5 mol % or less, or about 2 mol % or less, of trimelliticanhydride, trimellitic acid, pyromellitic dianhydride (pmda),pentaerythritol or other acids or diols that have more than two reactivesites may be incorporated as branching agents to increase the meltviscosity and improve the rheology for coextrusion in multilayerstructures. 3GT copolymers may contain at least about 85 mol %, at leastabout 90 mol %, at least about 95 mol %, or at least about 98 mol %, ofcopolymerized units of trimethylene terephthalate.

4GT homopolymers and copolymers are similar to 3GT, except thattetramethylene glycol (1,4-butanediol) is used in place of trimethyleneglycol in the polymers and are commercially available from DuPont underthe tradename CRASTIN or from BASF under the tradename ULTRADUR.

Because 3GT and 4GT polyesters are well known to one skilled in the art,the description of their preparation is omitted for the interest ofbrevity.

A polymer blend may comprise, for example, at least about 80%, or atleast about 90% of 3GT (and/or 4GT) homopolymer or copolymer, based onthe total weight of the blend composition. 3GT or 4GT polymer blend maycontain up to about 25% of one or more of the other polymers, based onthe total weight of the blend. Examples of other polymers may bepolyesters prepared from other diols, such as the diols described above.

A 3GT polymer may have an IV ranging from about 0.8 dl/g to about 1.4dl/g, or about 0.9 dl/g to about 1.1 dl/g, as measured using GoodyearR-103B Equivalent IV Method at a concentration of 0.4 g/dl in 50/50%trifluoroacetic acid/ dichloromethane, and a number average molecularweight (M_(n)) ranging from about 19,000 to about 45,000, or about25,000 to about 30,000.

The acid copolymers may be “direct” or “random” acid copolymers meaningpolymers polymerized by adding all monomers simultaneously, as distinctfrom a graft copolymer, where a monomer is grafted onto an existingpolymer, often by a subsequent free radical reaction.

An example of an acid copolymer is E/X/Y copolymer where E representscopolymerized units of ethylene, X represents at least one copolymerizedunsaturated carboxylic acid unit as disclosed above, and Y representscopolymerized units of a softening comonomer such as alkyl acrylate,alkyl methacrylate, or combinations thereof. X may be present in thecopolymer in amounts ranging from a lower limit of about 12 or 14 to anupper limit of about 19, 20, 22, 25, 30, or 35% of the E/X/Y copolymer.For example, methacrylic acid (MAA) may be present in an amount fromabout 12 to about 20% while acrylic acid (AA) may be present in anamount from about 12 to about 19%. Y may be present in the copolymer inamounts from 0 to about 28, 0.1 to 28, 0.1 to 10, 5 to 25, or 5 to 15%of the E/X/Y copolymer. E/X dipolymer has 0% of Y and X can be fromabout 12 to about 20, 25 or 35% of the dipolymer. E/X/Y copolymers canhave X from about 12 to about 20% and Y from about 4 to about 25% of thecopolymer.

The C₃₋₈ α,β-ethylenically unsaturated carboxylic acid may be acrylicacid or methacrylic acid or combinations thereof and the copolymerizedcomonomers of C₃ to C₈ α,β-ethylenically unsaturated carboxylic acidesters when present are C₁-C₈ alkyl esters of acrylic acid ormethacrylic acid.

Alkyl acrylates and alkyl methacrylates include alkyl groups having from1 to 4, or from 3 to 4, carbon atoms such as methyl acrylate, ethylacrylate, n-butyl acrylate, methyl methacrylate, ethyl methacrylate, andn-butyl methacrylate.

Specific acid copolymers include ethylene/acrylic acid dipolymers;ethylene/methacrylic acid dipolymers; ethylene/acrylic acid/methylacrylate terpolymers; ethylene/acrylic acid/methyl methacrylateterpolymers; ethylene/methacrylic acid/methyl acrylate terpolymers;ethylene/methacrylic acid/methyl methacrylate terpolymers;ethylene/acrylic acid/ethyl acrylate terpolymers; ethylene/acrylicacid/ethyl methacrylate terpolymers; ethylene/methacrylic acid/ethylacrylate terpolymers; ethylene/methacrylic acid/ethyl methacrylateterpolymers; ethylene/acrylic acid/n-butyl acrylate terpolymers;ethylene/acrylic acid/n-butyl methacrylate terpolymers;ethylene/methacrylic acid/n-butyl acrylate terpolymers; ethylene/methacrylic acid/n-butyl methacrylate terpolymers; or combinations oftwo or more thereof

The acid copolymers may be produced by any methods known to one skilledin the art such as that disclosed in U.S. Pat. No. 5,028,674. Becausesuch methods are so well known, their description is omitted herein forthe interest of brevity. The acid copolymers include those commerciallyavailable from DuPont under the tradename NUCREL.

Ethylene/acrylic acid dipolymers and ethylene/acrylic acid/alkylacrylate terpolymers are of note because acrylic acid may provide moreacid moieties than an equal weight of methacrylic acid. Mixtures of acidcopolymers may be used.

Melt processable ionomers may be prepared from acid copolymers describedabove by methods known in the art for preparing ionomers. They includepartially neutralized acid copolymers, particularly copolymers preparedfrom copolymerization of ethylene and acrylic acid or methacrylic acid.The ionomers may be neutralized by metal-containing bases to any levelthat does not result in an intractable (not melt processable) polymerthat does not have useful physical properties, for example, at leastabout 15% or at least about 20%, about 15 to about 70%, about 20 toabout 70%, or about 40 to about 70% of the acid moieties of the acidcopolymer are neutralized to form salts with sodium, magnesium, calciumor zinc cations, or combinations of such cations.

Unmodified ionomers include those commercially available from DuPontunder the tradename SURLYN. Unmodified ionomers comprising magnesium,zinc or calcium cations may be used to prepare the ionomer modifiercomposition by mixing with organic acids or salts thereof and optionallyfurther neutralizing as described below. Unmodified ionomers containingsodium cations may be mixed with the 3GT polyester modified with theionomer modifier composition as described below.

Organic acids can include, without limitation, aliphatic, monofunctionalorganic acids having 4 to 36 carbon atoms, optionally substituted withfrom one to three substituents independently selected from C₁ to C₈alkyl groups. The organic acids may be saturated or unsaturated, and, ifunsaturated, may include more than one carbon-carbon double bond.“Monofunctional” refers to acids with one carboxylic acid moiety. Thesuitable organic acids include C₄ to C₃₆ (for example C₁₈), C₆ to C₂₆,C₆ to C₁₁, or C₁₁ to C₁₆ acids.

Specific examples of suitable organic acids include, but are not limitedto, caproic acid, caprylic acid, capric acid, lauric acid, stearic acid,isostearic acid, behenic acid, montanic acid, erucic acid, oleic acid,iso-oleic acid, and linoleic acid. Naturally-derived organic fatty acidssuch as palmitic, stearic, oleic, erucic, behenic acids, or combinationsof two or more thereof.

Commercial grades of organic acids may include a number of structurallydifferent organic acids of varying lesser amounts. Therefore, acomposition that comprises a named acid may also include other acidsthat are present in commercial grades of the named acid, at levels thatare proportional to their levels in the commercial grade.

Saturated acids include stearic acid, montanic acid and behenic acid.Unsaturated linear organic acids include oleic acid and erucic acid. Thelongest carbon chain of the acid may be substituted with from one tothree C₁ to C₈ alkyl substituents such as methyl. Of note are saturated,branched organic acids wherein the longest carbon chain of the acid issubstituted with one C₁₋₈ alkyl group and an organic acid that isbranched and saturated, having from 6 to 24 carbon atoms, such asiso-stearic acid. The C₁₈ saturated branched organic acid, “iso-stearicacid,” is also known as iso-octadecanoic acid.

While it may be useful for the organic acids (and salts) to have a lowvolatility when being melt-blended with the acid copolymer or ionomer,volatility has been found to not be limiting when preparing blends withhigh nominal neutralization levels, particularly near or above 100%. Atabove 100% nominal neutralization (i.e., sufficient basic compound isadded such that all acid moieties in the copolymer and organic acid arenominally neutralized) or greater, volatility simply is no longer anissue. As such, organic acids with lower carbon content may be used. Itis preferred, however, that the organic acid (or salt) be non-volatileand non-migratory. By non-volatile, it is meant that they do notvolatilize at temperatures of melt blending of the agent with the acidcopolymer. By non-migratory, it is meant that the acid does not bloom tothe surface of the polymeric article under normal storage conditions atambient temperatures.

The organic acids may present in the modifier in a range having a lowerlimit of about 5% to an upper limit of about 60%, about 30 to about 50%,or about 35 to about 45% of the modifier combination (these amounts arebased on the amount of organic acid added to the combination in itsnon-neutralized or free-acid form).

The salts of the organic acids may be any of a wide variety,particularly including the zinc, magnesium or calcium salts of theorganic acids. Magnesium salts or calcium salts are preferred.

The organic acid salt and ionomer combination may be added to the 3GT or4GT polyester as individual components, or may be prepared as describedbelow and the combination then added to the polyester. When added asindividual components, the organic acid salt may be added to thepolyester in from about 0.1 to about 15% and the ionomer may be added tothe polyester in about 0.1 to about 15% such that the combination oforganic acid salt and ionomer is present in the polyester composition inabout 0.2 to about 30%.

Of note are 3GT or 4GT polyester compositions in which the combinationof organic acid salt and ionomer is present in a range from a lowerlimit of about 0.2, 0.5 or 1 to an upper limit of about 5, about 10,about 15, about 20 or about 30% of the total composition.

Modifier may be produced by heating a mixture of the ethylene acidcopolymer(s) or ionomer(s), the organic acid(s) or salt thereof, and atleast one basic compound capable of neutralizing the combined acidmoieties of the acid copolymer and the organic acid. For example, thecomponents of the composition may be mixed by (a) melt-blending ethyleneα,β-ethylenically unsaturated C₃₋₈ carboxylic acid copolymer(s) orionomer(s) thereof as described above that are not neutralized to thelevel that they have become intractable (not melt-processible) with oneor more organic acids as described above or salts thereof, andconcurrently or subsequently (b) adding a sufficient amount of a basiccompound capable of neutralization of the combined acid moieties(including those in the acid copolymer and in the organic acid), tonominal neutralization levels of about 75% to about 100% (or higher).

Treatment of acid copolymers and organic acids with basic compounds(concurrently or subsequently), without the use of an inert diluent, mayprepare the final composition without loss of processibility which wouldresult in loss of melt processibility for the 100% neutralized ionomeralone. For example, an acid copolymer blended with organic acid(s) maybe nominally neutralized to at least 100% without losing meltprocessibility. In addition, nominal neutralization to at least 100%reduces the volatility of the organic acids.

The acid copolymer(s) or unmodified, melt-processible ionomer(s) may bemelt-blended with the organic acid(s) or salt(s) and other polymers inany manner known in the art, such as melt-mixing. For example, atwin-screw extruder may be used to mix the acid copolymer and theorganic acid and treat with the basic compound at the same time. It isdesirable that the mixing is conducted so that the components areintimately mixed, allowing the basic compound to neutralize the acidicmoieties in the other components.

The amount of basic metal compound may be provided by adding thestoichiometric amount of the basic compound calculated to neutralize atarget amount of acid moieties in the acid copolymer and organic acid(s)in the blend (herein referred to as “% nominal neutralization” or“nominally neutralized”). Thus, sufficient basic compound is madeavailable in the blend so that, in aggregate, the indicated level ofnominal neutralization could be achieved.

Basic compounds can include formates, acetates, nitrates, oxides,hydroxides or alkoxides of the ions of alkaline earth metals andtransition metals. Examples include formate, acetate, hydroxide, oxide,alkoxide, etc. of magnesium or calcium.

The basic compounds may be added neat to the acid copolymer or ionomerthereof and the organic acid or salt thereof. The basic compound mayalso be premixed with a polymeric material, such as an acid copolymer,to form a “masterbatch” that may be added to the acid copolymer orionomer thereof and the organic acid or salt thereof. Of note is amasterbatch comprising about 40 to 60% of a copolymer of ethylene,acrylic acid or methacrylic acid, and optionally an alkyl acrylatewherein the alkyl group has from 1 to 4 carbon atoms; and about 40 to60% of a basic compound as described above (e.g., Mg(OH)₂).

It is desirable to run the blending/neutralization process with anextruder equipped with a vacuum port to remove any excess volatilesincluding moisture. Moisture may have a negative impact on subsequentmolding operations in that excess moisture and volatiles may createunwanted foaming and voids in the molded article.

Neutralization can provide the overall salt of the composition comprisesat least about 75, at least about 80%, at least about 90, or even 100%,equivalent % magnesium, calcium or zinc cations, based on the totalsalts present in the composition.

Polyester may be nucleated to improve crystallinity and heat resistance.For example, U.S. Pat. No. 6,245,844 discloses 3GT nucleated with amonosodium salt of a dicarboxylic acid selected from monosodiumterephthalates, monosodium naphthalene dicarboxylates, and monosodiumisophthalates. Suitable nucleation agents also include sodium salts ofC₁₀ to C₃₆ (e.g., C₁₈ to C₃₆, or C₃₀ to C₃₆) monofunctional organicacids, such as sodium stearate, sodium behenate, sodium erucate, sodiumpalmitate, sodium montanate, or combinations of two or more thereof.“Monofunctional” refers to acids with one carboxylic acid moiety.Nucleated polyesters such as nucleated 3GT may have crystallizationtemperatures up to 50° C. higher than that of the non-nucleatedpolyester. An example of a nucleator is the sodium salt of montanicacid, commercially available under the tradename LICOMONT NaV101 fromClariant.

About 0.005 to about 1% of a nucleating agent, either a monosodium saltof a dicarboxylic acid selected from monosodium terephthalates,monosodium naphthalene dicarboxylates, monosodium isophthalates, or asodium salt of a C₁₀ to C₃₆ monofunctional organic acid, can be includedto the compositions. Higher molar levels, than those disclosed, ofsodium salts of organic acids may lead to reduced molecular weight whichreduces melt viscosity, but leads to inferior mechanical properties.Shorter-chain acid salts require lower amounts by weight to minimizemolecular weight reduction. Of note is a composition as described hereincomprising about 0.1 to about 1% of a nucleator, for example a sodiumsalt of a C₃₀ to C₃₆ monofunctional organic acid.

Nucleated polyester containing mono-sodium terephthalate or a sodiumsalt of a C₁₀ to C₃₆ monofunctional organic acid exhibit shortcrystallization half times and early onsets of crystallization asmeasured by differential scanning calorimeter (DSC) in the heating andcooling cycle. These are desirable effects because the nucleatedpolymers may quickly become rigid, leading to faster demold times andshorter cycle times in processing the polymers into shaped articles bysuch methods as thermoforming, injection molding, and blow molding. Inaddition, polyester polyester containing mono-sodium terephthalateexhibited significant improvement in brittleness, heat resistance, andimpact resistance over the non-nucleated polyester.

In contrast to 3GT polymers, 4GT polymers are normally sufficientlycrystalline that they do not need to be nucleated to provide suitablehigh temperature performance.

Toughening polyester may be achieved using an ionomer modifier, or acombination of ionomer and an epoxide-containing copolymer such asEBAGMA copolymers or ethylene/glycidyl methacrylate (EGMA) copolymers.The modifiers provided increased toughness and lower flex modulus, butthe melt viscosity of the blends was increased, which is undesirable forsome molding applications. Other tougheners useful in the compositionsdescribed herein include ethylene/alkyl acrylate copolymers orethylene/alkyl methacrylate copolymers.

Use of the modifier combination may reduce the viscosity of polyestercompositions, including those toughened with epoxide-containingcopolymers, non-epoxide-containing copolymers or combinations of both.

When the composition comprises ethylene ester copolymer toughener(s),the ionomer/organic acid salt combination may be about 0.2 to about 15%based on the combination of (a) and (b).

The ethylene ester copolymers may also be created bygraft-copolymerization of the ester comonomer onto a previouslypolymerized ethylene copolymer. The comonomer copolymerized withethylene can be selected from the group consisting of methyl acrylate,ethyl acrylate, n-butyl acrylate, glycidyl methacrylate and combinationsof two or more thereof.

The ethylene ester copolymer may comprise, based on the total weight ofthe ethylene ester copolymer, about 60 to about 95%, about 60 to about90%, or about 70 to about 90%, of ethylene; about 0.5 to about 25%,about 2 to about 20%, or about 3 to about 17%, of ester comonomer offormula (iii); and up to about 40%, about 3 to about 70%, about 3 toabout 40%, about 15 to about 35%, or about 20 to about 35 %, of estercomonomer of formula (iii).

Specific examples of the ethylene ester copolymers include dipolymersproduced by the copolymerization of ethylene and an alkyl acrylate oralkyl methacrylate such as methyl acrylate, ethyl acrylate or butylacrylate (EBAGMA and EGMA). Additional comonomers may be present ascopolymerized units in the ethylene copolymers. For example, theethylene ester copolymers may additionally comprise other comonomerssuch as carbon monoxide. When present, copolymerized units of carbonmonoxide may comprise up to about 20%, or about 3 to about 15% of theweight of the ethylene ester copolymer.

The ethylene ester copolymers may be prepared by any suitable process.In particular, the ethylene ester copolymers may be prepared bypolymerization of the foregoing monomers in the presence of afree-radical polymerization initiator at elevated temperatures (e.g.,about 100° C. to about 270° C. or about 130° C. to about 230° C.) andelevated pressures (e.g., at least about 70 MPa or about 140 to about350 MPa) and the polymerization may be carried out by a) a batch processin a conventional autoclave, or b) a continuous process in a series ofautoclaves or a multi-zoned autoclave or a tubular reactor (see, e.g.,U.S. Pat. Nos. 3,350,372, 3,756,996, 5,532,066, 5,543,233, and5,571,878). The ethylene ester copolymers may be homogeneous or not. Forexample, the ethylene ester copolymers may not be homogeneous in termsof concentration of monomer units along the polymer chain due toimperfect mixing during polymerization or variable monomerconcentrations during the course of the polymerization.

The ethylene ester copolymer can be selected from the group consistingof ethylene/methyl acrylate dipolymer, ethylene/ethyl acrylatedipolymer, ethylene/n-butyl acrylate dipolymer, ethylene/glycidylmethacrylate dipolymer, ethylene/n-butyl acrylate/glycidyl methacrylateterpolymer, ethylene/n-butyl acrylate/carbon monoxide terpolymer andcombinations of two or more thereof.

Ethylene/glycidyl methacrylate dipolymers can include those comprisingabout 0.5 to about 25%, or about 2 to about 20,% of glycidylmethacrylate. Ethylene/n-butyl acrylate/glycidyl methacrylateterpolymers can include those comprising about 0.5 to about 25 or about2 to about 20% of glycidyl methacrylate, and about 3 to about 40% ofn-butyl acrylate.

An ethylene/alkyl acrylate copolymer can comprise from about 20 to about30% of methyl acrylate as the alkyl acrylate component. Suitableethylene/alkyl acrylate copolymers, for example, comprise 24%, 25% or30% of methyl acrylate. Ethylene/alkyl acrylate copolymers arecommercially available from DuPont under the ELVALOY AC tradename. Otherethylene alkyl acrylate copolymers may also be suitable.

Any physical forms, such as pellets, of 3GT or 4GT may be used. Afterbeing optionally blended or coated with any desired additives by, e.g.,drying mixing to produce a mixture, the mixture can be further blendedwith a nucleating agent, preferably by melt blending such as with anextruder. The blending temperature, e.g., barrel temperature of anextruder barrel, may be raised from a cold feed to about 250° C. toabout 265° C. and the mixture may be conveyed forward to a mixing zonenear the front end of the extruder. The mixing zone may have kneadingblocks for mixing to provide a well dispersed mixture. The extrudate maybe quenched in a water bath and the cut into pellets. The pellets may bedried and tested for melt viscosity and molded into articles.

The modified 3GT or 4GT compositions may optionally include from about 1to about 30% of other (unmodified) ionomers containing sodium cations.Addition of sodium ionomers to 3GT polyester in combination with themagnesium, calcium or zinc-containing organic acid modified ionomer mayprovide desirable combinations of physical properties. For example, meltviscosity of the modified 3GT composition may be adjusted to a desiredlevel by employing a mixture of sodium ionomer and magnesium organicacid modified ionomer. Tensile properties such as elongation to breakand modulus may also be affected. Higher crystallization temperatures ofthe modified 3GT composition may be maintained by using a sodium ionomerand the magnesium organic acid modified ionomer.

Of note are optional sodium ionomers of E/X dipolymers wherein X is fromabout 12 to about 20, 25 or 35% of the dipolymer. These ionomers may beuseful in providing compositions exhibiting strain hardening instress-strain tests discussed below, particularly when added in at least15% of the total composition. Also of note are optional sodium ionomersof E/X/Y copolymers wherein X is from about 3 to about 12% and Y is fromabout 4 to about 25% of the copolymer.

The compositions may additionally comprise from 0.001 to 15%, or from0.01 to 10%, of the total composition, of one or more additivesincluding plasticizers, stabilizers including viscosity stabilizers andhydrolytic stabilizers, primary and secondary antioxidants (e.g.,hindered phenols characterized as phenolic compounds that containsterically bulky radicals in close proximity to the phenolic hydroxylgroup or IRGANOX 1010), ultraviolet ray absorbers and stabilizers,anti-static agents, dyes, pigments or other coloring agents,fire-retardants, lubricants, processing aids, slip additives, antiblockagents such as silica or talc, release agents, and/or mixtures thereof.Additional optional additives may include inorganic fillers; acidcopolymer waxes, such as for example Honeywell wax AC540; TiO₂, which isused as a whitening agent; optical brighteners; surfactants; and othercomponents known in the art to be useful additives. These additives aredescribed in the Kirk Othmer Encyclopedia of Chemical Technology. Ofnote is a composition as described herein comprising about 0.1 to about1% of an antioxidant.

Waxes used as processing aids are low molecular weight (less than about10,000 daltons), low melting materials. Of note is a composition asdescribed herein comprising about 0.1 to about 1% of wax.

3GT or 4GT polyesters may also contain inorganic fillers such as glassfibers, talc, and/or other mineral reinforcements to increase thestiffness and heat resistance of the compositions.

The optional incorporation of these additives into the compositions maybe carried out by any known process, for example, by dry blending,extruding a mixture of the various constituents, the conventionalmasterbatch technique, or the like.

A film may be made from the composition by melt-processing using knownprocesses such as co-extrusion, sheet extrusion, extrusion casting,extrusion coating, thermal lamination, blown film methods, or any knownprocesses. Because the processes for making films are well known to oneskilled in the art, the description is omitted herein for the interestof brevity.

The compositions may be useful for molding small and/or thin-walledarticles. The thin-walled articles may be about 0.5 mm to about 1 mmthick, or thicker.

The toughened compositions are useful for high-sheer, high-throughputinjection molding applications. Molded articles may be produced from acomposition disclosed above, by virtually any method of extrusionprocessing known to those skilled in this art. For example, a meltextrusion process such as injection molding, coinjection molding,compression molding, overmolding or profile extrusion may be used. Assuch, the articles may be injection molded, compression molded, profileextruded or the like. Injection molded articles are of note. Inaddition, the shaped articles may comprise material other than themodified polyester, such as layers of polymeric material other than themodified polyester including the presence of tie (adhesive) layers andthe like, or nonpolymeric substrates. For example, articles may beprepared by coinjection molding wherein two melt streams are injectedinto a mold in such a way that one polymer (often, the more expensiveand/or more functional polymer) is on the exterior of the article whilethe lower cost, lower performing polymer is in the interior.

One or more additives disclosed above may be present in the respectivelayers.

Various injection-molded articles may be prepared including smallhousehold items and parts for machinery and vehicles. Household andpersonal items include combs and other hair setting and stylingutensils, other personal care utensils, eyeglass frames, telephones,computer housings, keypads and mouse units, writing utensils, flatware,calculators, cameras, pails, garbage containers, game boards and pieces,toys, credit cards, and furniture, and tool handles. Machine and vehicleparts such as steering wheels, handles, knobs, and the like may beprepared. Containers and caps may also be prepared from the modified 3GTresin.

Molded articles include caps or closures comprising a compositiondisclosed above. Caps may be compression molded or injection molded.Such caps may be used to close and seal a wide variety of containers forbeverages (e.g., carbonated soft drinks and pasteurized beverages);foods (e.g., oxygen sensitive ones such as mayonnaise, peanut butter andsalad oil, and including corrosive ones such as vinegar, lemon juice);and household chemicals (e.g., bleaches, detergents, personal hygieneproducts, medicaments, drugs, cosmetics, petroleum products, and otherproducts).

Containers include bowls, trays, cups, cans, buckets, tub, boxes, vials,bottles, vials, jars and other containers may be prepared, for example,by injection molding.

Another example of a shaped article is a profile. Profiles have aparticular shape and by their process of manufacture known as profileextrusion. Profiles are not film or sheeting, and thus the process formaking profiles does not include the use of calendering or chill rolls.Profiles are also not prepared by injection molding processes. Becauseprofile processing is well known, the description of which is omittedherein for the interest of brevity.

Overmolding of a substrate such as a metal insert, shaped polymeric partor combination thereof with the modified 3GT or 4GT polyester alsoproduces shaped articles comprising an outer layer of the modified 3GTor 4GT polyester. Alternatively, the 3GT or 4GT composition as describedherein may be used as a substrate that may be overmolded with otherpolymeric materials. Because overmolding is well known, the descriptionof which is omitted herein for the interest of brevity.

Articles prepared from 4GT polymers may include one or more belts,boards, automobile parts and electronic or electrical connectors; theautomobile part includes air bag plug, automobile lighting hardware,auto lamp sockets and bases, auto air intake duct, or combinations oftwo or more thereof; the electrical or electronic part includes one ormore electrical or electronic connectors or capacitors used under thehood of an automobile or electrical relay component, relay base, relaycase, ignition system component, or combinations of two or more thereof.The methods described above for preparation of 3GT articles are alsouseful in preparing 4GT articles.

EXAMPLES

The Examples are illustrative and are not to be construed as to undulylimit the scope of the invention.

Materials Used

-   3GT-1: A 3GT homopolymer available commercially under the tradename    SORONA from DuPont.-   4GT-1: A 4GT homopolymer available commercially under the tradename    CRASTIN 6131 from DuPont.-   M-1: a blend of 60% of an ethylene/acrylic acid/n-butyl acrylate    terpolymer (8.5% AA and 15.5% n-BA) and 40% of magnesium stearate,    neutralized to about 100% with magnesium.-   M-2: a blend of 60% of an ethylene/methacrylic acid dipolymer (19%    MAA) and 40% of sodium stearate, neutralized to about 100% with    sodium.-   M-3: a blend of 70% of an ethylene/acrylic acid/n-butyl acrylate    terpolymer (6.2% AA and 28% n-BA) with MI of 210 g/10 min. and 30%    of sodium behenate, neutralized to about 100% with sodium.-   I-1: an ethylene/methacrylic acid dipolymer (15% MAA), neutralized    with Na (59%), MI of 0.9 g/10 min.-   I-2: an ethylene/methacrylic acid dipolymer (15% MAA), neutralized    with Zn (58%), MI of 0.7 g/10 min.-   I-3: an ethylene/methacrylic acid dipolymer (19% MAA), neutralized    with 2.5 weight % Mg(OH)₂, MI of 1.1 g/10 min.-   I-4: an ethylene/methacrylic acid terpolymer (9% MAA, 23% of n-butyl    acrylate), neutralized with Na (52%), MI of 1.0 g/10 min.-   EMA-1: an ethylene/methyl acrylate dipolymer (30% MA), MI of 3 g/10    min.-   EBAGMA-1: a terpolymer of 70% of ethylene/25% of n-butyl acrylate/5%    of glycidyl methacrylate.-   Nuc-1: sodium montanate obtained from Clariant under the tradename    LICOMONT NaV101.-   AO-1: bis-(2,4-di-t-butylphenyl) pentaerythritol diphosphite    antioxidant available from Chemtura under the tradename ULTRANOX    626.-   Wax: processing wax available commercially as AC Wax 16A,    (Honeywell, Morristown, N.J.).-   MgSt: Magnesium stearate, commercial grade.

Pellets of 3GT-1 homopolymer, coated with antioxidant AO-1 and nucleatorNuc-1 and dried to give pellets of Comparative Example C2, or the dried3GT-1 pellets were shaken with powders of AO-1 and Nuc-1 to provide thedry-coated pellets. The dried pellets of 3GT-1 homopolymer, coated withantioxidant and nucleator, were added to the back end of a W & P twinscrew extruder along with pellets of the modifier(s). The barreltemperature of the extruder barrels was raised from a cold feed to about250° C. and the pellets conveyed forward to a mixing zone near the frontend of the extruder. The mixing zone had kneading blocks to mix theingredients and the zone had a “reverse” element to create a sealbetween the extruder barrel and the extruder screw elements. The reverseelement pumped the melt momentarily backwards. The seal allowed vacuumto be applied at the next barrel section so that volatiles were removed.The barrel temperatures were then dropped to about 240° C. and the diewas also set to that temperature range. This provided a well dispersedmixture, with melt temperature of around 255 to 265° C. The compositionsthat were prepared are summarized in Table 1A and 1 B wherein theamounts are reported in weight %.

Ingredients were fed to twin screw extruder and the strand extrudate wasquenched in a water bath and the strand was cut into pellets. Thepellets were dried and tested for viscosity, crystallization behaviorand molded using an Arburg injection molding machine. D1708 tensile barswere made and used in stress/strain measurements.

TABLE 1A Example 3GT-1 Nuc-1 AO-1 I-1 I-2 I-3 I-4 M-1 M-2 M-3 MgSt Wax 196.4 0.5 0.1 0 0 0 0 3 0 0 0 0 2 79.5 0.5 0 0 0 0 0 20 0 0 0 0 3 88.40.5 0.1 0 0 10 0 1 0 0 0 0 4 86.4 0.5 0.1 10 0 0 0 3 0 0 0 0 5 76.4 0.50.1 20 0 0 0 3 0 0 0 0 6 76.3 0.5 0.2 15 15 0 0 3 0 0 0 0 7 97.9 0.5 0.10 0 0 0 1 0 0 0 0.5 8 78.8 0.5 0.2 0 0 0 0 20 0 0 0 0.5 9 78.9 0.5 0.1 00 0 0 20 0 0 0 0.5 10 77.9 0.5 0.1 0 0 0 20 1 0 0 0 0.5 11 78.8 0.5 0.20 0 0 19 1 0 0 0 0.5

TABLE 1B Example 3GT-1 Nuc-1 AO-1 I-1 I-2 I-3 I-4 M-1 M-2 M-3 MgSt WaxC1 100 0 0 0 0 0 0 0 0 0 0 0 C2 99.4 0.5 0.1 0 0 0 0 0 0 0 0 0 C3 79.40.5 0.1 20 0 0 0 0 0 0 0 0 C4 89.4 0.5 0.1 0 0 10 0 0 0 0 0 0 C5 98.40.5 0.1 0 0 0 0 0 1 0 0 0 C6 96.4 0.5 0.1 0 0 0 0 0 3 0 0 0 C7 89.4 0.50.1 0 0 0 0 0 0 10 0 0 C8 86.4 0.5 0.1 0 0 0 0 3 10 0 0 0 C9 98.9 0.50.1 0 0 0 0 0 0 0 0.5 0 C10 0 0 0 0 0 0 0 100 0 0 0 0 C11 98.8 0.5 0.2 00 0 0 0 0 0 0 0.5

Additional examples were prepared using modifier M-1 and ethylene estercopolymers as summarized in Table 2.

TABLE 2 Example 3GT-1 Nuc-1 AO-1 M-1 EMA-1 EBAGMA-1 C12 89.4 0.5 0.1 0 55 12 93.4 0.5 0.1 1 5 0 13 88.4 0.5 0.1 1 10 0 14 84.4 0.5 0.1 10 0 5 1574.4 0.5 0.1 20 0 5 16 69.4 0.5 0.1 20 0 10 17 84.9 0 0.1 10 0 5 18 79.40.5 0.1 10 0 10 19 88.4 0.5 0.1 1 5 5

Melt rheology was measured on a piston rheometer (Dynisco CapillaryRheometer, Model LCR 7000) run at constant temperature (260° C.), withsamples having from 100 to 150 ppm moisture. Sample pellets wereintroduced into the chamber, thermally equilibrated and melted for sixminutes. Pressure was applied to the pellets to eliminate air pockets.After six minutes force was applied to the pellets to achieve a seriesof selected shear rates and the force required to achieve the shear ratewas measured and the resultant melt viscosity determined. Table 3reports the melt viscosity at 1000 sec⁻¹.

As summarized in Table 3, compositions comprising 3GT-1 and variousmodifiers were prepared and their Mn, Mw and Mz were measured usingcolumn chromatography according to standard protocols used in molecularweight determinations. Mn is the number average molecular weight; Mw isthe weight average molecular weight and Mz is the z “moment” averagemolecular weight.

TABLE 3 Melt Viscosity Example (Pa · sec) at 1000 sec⁻¹ Mw Mn Mz C1 14549,930 23,140 75,870 C2 140-150 46,430 23,500 69,900 C3 175-215 C4 183C5 118 41,340 19,860 62,410 C6 89 39,460 19,600 59,200 C7 58 27,68013,830 42,360 C8 52 35,790 18,060 53,310 C9 57 46,910 22,070 71,210  C10118  1 33 43,630 19,750 67,500  2 25 48,000 23,600 74,200  3 36  4 30-6045,010 23,120 66,370  5 60  6 89  C11 111  7 65 47,510 22,920 72,210  819  9 30 10 123 48,300 24,250 72,310 11 —  C12 148 12 83 13 60 14 77 1595 16 98 17 41 18 25 19 100

Addition of unmodified ionomers to 3GT-1 has minimal effect on viscosityat low addition levels (for example, the melt viscosity for acomposition with 1% of I-1 is 146, and with 2% of I-1 is 149), but 10 to20% of unmodified ionomers raises the melt viscosity, as demonstrated byComparative Examples C3 and C4. Organic acid salt modified ionomers withsodium cations provided lower melt viscosity but significantly reducedmolecular weight (Comparative Examples C5, C6 and C7 and C8). Withoutbeing bound by theory, the relatively large amount of sodium organicacid salt in these Comparative Examples may have led to the molecularweight reduction. Magnesium stearate modified 3GT-1, Comparative ExampleC9, provided reduced viscosity without significantly reducing molecularweight, but provided incomplete crystallization on cooling a sample (seebelow).

The Examples, compositions of the invention, show that organic acid saltmodified ionomers with non-sodium (for example Mg) cations provide lowermelt viscosity without significantly reducing molecular weight orsignificantly reducing crystallization temperature. The reduction ofmelt viscosity provided by the Examples is greater than would beexpected by an arithmetic combination of the melt viscosities ofComparative Example C2 and Comparative Example C10.

Addition of the organic acid salt modified ionomers to blends containingunmodified sodium ionomers also lowers viscosity (Compare ComparativeExample C3 with Examples 4, 5 and 6 and Comparative Example C4 withExample 3.

Use of a wax modifier (Comparative Example C11) also reduced meltviscosity, but provided poor elongation at break (see below). Elongationat break was improved when an organic acid salt modified ionomer withmagnesium cations was added, while maintaining low melt viscosity(Examples 8 and 9).

The extent of crystallization of modified 3GT-1 samples was measuredaccording to the following procedure. Crystallization exothermmeasurements were conducted on a TA Instruments (New Castle, Del.) ModelQ1000 and operated on about 5 to 10 mg of sample. The polymer sample wasmelted in a standard DSC test, heating the sample to 260° C. at 10°C./minute. The sample was then cooled at 10° C./minute and reheated to260° C. at 10° C./minute. If the polymer is cooled from the melt, andthe DCS trace shows an exotherm peak on subsequent heating, the sampleis not fully crystallized. This peak is a crystallization peak of thepolymer that did not crystallize as the original melt was cooled. DSCtraces for the Examples in Table 4 showed no exotherm peaks on first orsecond DSC heat cycles (except Sample C9), indicating they werecrystallized fully on cooling at this rate (10° C./minute). Sample C9showed such a peak at about 70° C. of 30 J/gm heat content, indicatingquenching (incomplete crystallization) during the cooling process.

TABLE 4 Example Crystallization* C1 158 C2 200  4 203  5 203  6 193 C11202  8 184  9 184 10 199 11 199 C12 202 12 196 13 186 19 182.5 C9 184*DSC temperature at maximum point on the exotherm curve on cooling frommelt temperature of 260° C., with cooling rate of 10° C./minute.

Tensile tests may be done at a temperature (about 90° C.) above theglass transition point (Tg) of the composition but below its meltingpoint, to evaluate potential thermoforming capability. Compositionssuitable for thermoforming desirably have functionality requirementssuch as strain hardening at elevated temperature (above Tg) (i.e., thefinal strength is greater than yield strength) exhibit an increase intensile modulus greater than the yield (of about 2000 psi), such thatwith further elongation, the tensile values exceed the yield pointtensile values. Thermoformable compositions also desirably have fastcrystallization and a high onset of crystallization temperature oncooling from the melt. This allows the formed sheet to be extensivelycrystallized so subsequent heating above the Tg (to about 90° C.) doesnot induce significant additional crystallization, which may causedistortion of the sheet prior to thermoforming.

Tensile strength and elongation at break were measured according to ASTMD1708 and summarized in Table 5 (90° C. Stress-Strain).

TABLE 5 elongation at Modulus Modulus Modulus Modulus Elongation maxtensile Example at 100% at 200% at 300% at break at break (%) (%)  43995 15 15  5 3220 3230 3870 4115 350 350  6 strain hardening 335 335C11 4955 17 17  8 2120 2700 3445 4020 455 455 10 no strain hardening 25520 11 no strain hardening 255 20 12 no strain hardening 180 20 13 nostrain hardening 205 18

Comparative Example C11 in the 90° C. tensile test showed maximumtensile strength of 4955 psi at 17% elongation, elongation at break was17. DSC test showed maximum exotherm on the cooling curve at 202° C. Itshowed good crystallization behavior, but had very poor elongation andno strain hardening. Example 4, with 3% of the modifier combination and10% of sodium ionomer also showed no strain hardening. Examples 10 and11 contained a sodium ionomer based on a low acid ethylene acidcopolymer (less than 12% methacrylic acid) and showed no strainhardening. Examples 12 and 13 contained ethylene/methyl acrylatecopolymer but no additional ionomer and also did not show strainhardening. However, Examples 5 and 6, with 3% of the modifiercombination and at least 15% of sodium ionomer(s) based on low acidethylene acid copolymers (more than 12 wt % methacrylic acid) did showstrain hardening. Example 8 also showed strain hardening.

Notched Izod tests were conducted according to ASTM procedure D256 andISO 180. Gardner Impact measurements were conducted according to ASTMprocedures D4226, D5420 and D5628.

TABLE 6 Example Gardner impact (inch-lb) Notched Izod (ft-lb/in) C2 320.4 to 0.5 C5 40 C6 16 C9 40  C10 88  7 40  C12 104  0.9 12 128  13 178 14 320* 15 320* 16 320* 17 320* 18 320* 19 120  1.1 *Highest valuepossible using the test conditions.

Compositions modified with the ionomer organic acid salt combinationshow good impact strength as demonstrated by Gardner impact tests.Compositions that also include EBAGMA-1 showed excellent impactstrength.

Pellets of 4GT-1 homopolymer were melt blended with antioxidant AO-1 andpellets of the modifier(s) in a W & P twin screw extruder to providewell dispersed mixtures. The compositions that were prepared aresummarized in Table 7 wherein the amounts are reported in weight %.

TABLE 7 Example 4GT-1 AO-1 M-1 EMA-1 EBAGMA-1 C13 99.9 0.1 0 0 0 20 84.90.1 10 0 5 21 79.9 0.1 10 5 5

The compositions were processed into test samples and tested asdescribed above for the 3GT compositions. Test results are summarized inTable 8.

TABLE 8 Melt Viscosity Notched Izod Example (Pa · sec) at 1000 sec⁻¹(ft-lb/in) C13 134 0.5 20 48 1.05 21 64 1.42

Examples 20 and 21, containing the modifier combination and ethyleneester copolymer tougheners, provided lower melt viscosity and greatertougheness than Comparative Example C13.

While certain of the preferred embodiments of the invention have beendescribed and specifically exemplified above, it is not intended thatthe invention be limited to such embodiments. Various modifications maybe made without departing from the scope and spirit of the invention, asset forth in the following claims.

1. A thermoplastic composition comprising or produced from, based on theweight of the thermoplastic composition, about 70 to about 99.8% of apolyester composition and a modifier wherein the polyester compositioncomprises poly(trimethylene terephthalate) or poly(tetramethyleneterephthalate), or combinations thereof; the modifier comprises at leastone aliphatic, monofunctional organic acid, at least one ionomer derivedfrom an ethylene acid copolymer, and optionally at least one ethyleneester copolymer; the organic acid has 4 to 36 carbon atoms, optionallysubstituted with a C₁₋₈ alkyl group; the acid copolymer comprisescopolymerized comonomers of ethylene, a copolymerized comonomers of atleast one C₃₋₈ α,β-ethylenically unsaturated carboxylic acid, andoptionally a copolymerized comonomer of at least one C₃₋₈α,β-ethylenically unsaturated carboxylic acid ester; the ethylene estercopolymer wherein comprises, based on the weight of the ethylene estercopolymer, (i) about 20 to about 95% of copolymerized units of ethylene,(ii) 0 to about 25% of copolymerized units of at least one ester of theformula CH₂═C(R¹)CO₂R², and (iii) 0 to about 80 weight % ofcopolymerized units of at least one ester of the formula CH₂═C(R³)CO₂R⁴;(ii) and (iii) cannot both be 0 weight %; R¹ is hydrogen or an alkylgroup having 1 to 6 carbon atoms; R² is a glycidyl group; R³ is hydrogenor an alkyl group having 1 to 8 carbon atoms; and R⁴ is an alkyl grouphaving 1 to 8 carbon atoms; from about 75% to about 100% of the combinedacid moieties in the modifier are neutralized to form salts with metalcations; and the cations comprise at least about 75 equivalent % ofmagnesium, calcium, zinc, or combinations of two or more thereof.
 2. Thecomposition of claim 1 wherein the organic acid is present in about 5 toabout 60 wt % of the modifier; the acid copolymer comprises, based onthe weight of the acid copolymer, about 3 to about 35 weight % of theC₃₋₈ α,β-ethylenically unsaturated carboxylic acid, and 0 to about 30weight % of the C₃₋₈ α,β-ethylenically unsaturated carboxylic acidester, and the remainder being ethylene; the C₃₋₈ α,β-ethylenicallyunsaturated carboxylic acid is acrylic acid, methacrylic acid, orcombinations thereof; and the C₃₋₈ α,β-ethylenically unsaturatedcarboxylic acid ester, when present, is a C₁-C₈ alkyl ester of acrylicacid or of methacrylic acid.
 3. The composition of claim 2 wherein theacid copolymer comprises 4 to 25 weight % of C₃₋₈ α,β-ethylenicallyunsaturated carboxylic acid ester.
 4. The composition of claim 2 whereinthe polyester composition is the poly(tetramethylene terephthalate). 5.The composition of claim 4 wherein the modifier further comprises about5 to 15 weight %, based on the weight of the thermoplastic composition,of at least one ethylene ester copolymer selected from the groupconsisting of ethylene/methyl acrylate dipolymer, ethylene/ethylacrylate dipolymer, ethylene/n-butyl acrylate dipolymer,ethylene/glycidyl methacrylate dipolymer, ethylene/n-butylacrylate/glycidyl methacrylate terpolymer, ethylene/n-butylacrylate/carbon monoxide terpolymer, and combinations of two or morethereof.
 6. The composition of claim 5 wherein the ethylene estercopolymer is an ethylene/glycidyl methacrylate dipolymer,ethylene/n-butyl acrylate/glycidyl methacrylate terpolymer, orcombinations thereof.
 7. The composition of claim 4 wherein the modifiercomprises a combination of an ethylene/alkyl acrylate dipolymer and anethylene/glycidyl methacrylate dipolymer, an ethylene/n-butylacrylate/glycidyl methacrylate terpolymer, or combinations thereof. 8.The composition of claim 2 wherein the polyester composition comprisesthe poly(trimethylene terephthalate) and about 0.005 to about 1 weight%, based on the total weight of the thermoplastic composition, of anucleating agent including a sodium salt of a carboxylic acid.
 9. Thecomposition of claim 8 wherein the nucleating agent is monosodiumterephthalate, monosodium naphthalene dicarboxylate, monosodiumisophthalate, a salt of a C₃₀ to C₃₆ monofunctional organic acid, orcombinations of two or more thereof and is present in 0.005 to 1 weight% of the thermoplastic composition.
 10. The composition of claim 8wherein the modifier further comprises about 5 to 15 weight %, based onthe weight of the thermoplastic composition, of at least one ethyleneester copolymer selected from the group consisting of ethylene/methylacrylate dipolymer, ethylene/ethyl acrylate dipolymer, ethylene/n-butylacrylate dipolymer, ethylene/glycidyl methacrylate dipolymer,ethylene/n-butyl acrylate/glycidyl methacrylate terpolymer,ethylene/n-butyl acrylate/carbon monoxide terpolymer, and combinationsof two or more thereof.
 11. The composition of claim 9 the modifierfurther comprises about 5 to 15 weight %, based on the weight of thethermoplastic composition, of an ethylene/methyl acrylate dipolymer, anethylene/glycidyl methacrylate dipolymer, ethylene/n-butylacrylate/glycidyl methacrylate terpolymer, or combinations of two ormore thereof.
 12. The composition of claim 9 wherein the modifiercomprises a combination of an ethylene/alkyl acrylate dipolymer and anethylene/glycidyl methacrylate dipolymer, an ethylene/n-butylacrylate/glycidyl methacrylate terpolymer, or combinations thereof. 13.The composition of claim 12 wherein the modifier further comprises fromabout 1 to about 30 weight %, based on the weight of the thermoplasticcomposition, of one or more additional ionomers containing sodiumcations.
 14. A shaped article comprising the composition of claim
 2. 15.A method comprising melt mixing a first polyester composition with amodifier under a condition effective to produce a second polyesterhaving a melt viscosity at least 10% less than that of the firstpolyester composition and a number average molecular weight of at least85% of that of the first polyester composition wherein the firstpolyester composition comprises poly(trimethylene terephthalate) orpoly(tetramethylene terephthalate), or combinations thereof; themodifier comprises at least one aliphatic, monofunctional organic acid,at least one ionomer derived from an ethylene acid copolymer, andoptionally at least one ethylene ester copolymer; the organic acid has 4to 36 carbon atoms, optionally substituted with a C₁₋₈ alkyl group andis present in about 5 to about 60 wt % of the modifier; the acidcopolymer comprises copolymerized comonomers of ethylene, acopolymerized comonomers of at least one C₃₋₈ α,β-ethylenicallyunsaturated carboxylic acid, and optionally a copolymerized comonomer ofat least one C₃₋₈ α,β-ethylenically unsaturated carboxylic acid ester;the ethylene ester copolymer wherein comprises, based on the weight ofthe ethylene ester copolymer, (i) about 20 to about 95% of copolymerizedunits of ethylene, (ii) 0 to about 25% of copolymerized units of atleast one ester of the formula CH₂═C(R¹)CO₂R², and (iii) 0 to about 80weight % of copolymerized units of at least one ester of the formulaCH₂═C(R³)CO₂R⁴; (ii) and (iii) cannot both be 0 weight %; R¹ is hydrogenor an alkyl group having 1 to 6 carbon atoms; R² is a glycidyl group; R³is hydrogen or an alkyl group having 1 to 8 carbon atoms; and R⁴ is analkyl group having 1 to 8 carbon atoms; from about 75% to about 100% ofthe combined acid moieties in the modifier are neutralized to form saltswith metal cations; and the cations comprise at least about 75equivalent % of magnesium, calcium, zinc, or combinations of two or morethereof.
 16. The method of claim 15 wherein the first polyestercomposition comprises the poly(tetramethylene terephthalate) polyester.17. The method of claim 15 wherein the first polyester compositioncomprises the poly(trimethylene terephthalate) polyester; the processfurther comprises melt mixing the first polyester composition with anucleating agent to produce a nucleated poly(trimethyleneterephthalate); and then melt mixing the nucleated poly(trimethyleneterephthalate) with the modifier wherein the nucleating agent ismonosodium terephthalate, monosodium naphthalene dicarboxylate,monosodium isophthalate, a salt of a C₃₀ to C₃₆ monofunctional organicacid, or combinations of two or more thereof; the nucleating agent ispresent in an effective amount such that is present in the range of fromabout 0.005 to about 1 weight % in the second polyester composition. 18.The method of claim 15 wherein the modifier comprises the ethylene estercopolymer including an ethylene/methyl acrylate dipolymer, anethylene/glycidyl methacrylate dipolymer, ethylene/n-butylacrylate/glycidyl methacrylate terpolymer, or combinations of two ormore thereof.
 19. The method of claim 16 wherein the modifier comprisesthe ethylene ester copolymer including an ethylene/methyl acrylatedipolymer, an ethylene/glycidyl methacrylate dipolymer, ethylene/n-butylacrylate/glycidyl methacrylate terpolymer, or combinations of two ormore thereof.
 20. The method of claim 17 wherein the modifier comprisesthe ethylene ester copolymer including an ethylene/methyl acrylatedipolymer, an ethylene/glycidyl methacrylate dipolymer, ethylene/n-butylacrylate/glycidyl methacrylate terpolymer, or combinations of two ormore thereof.